In the present case, a surgical microscope is understood to mean a system with a microscope unit, preferably embodied as a stereo microscope, which is received at a stand and which enables an observing person to observe an operating region with magnification. The microscope unit can be configured for visualizing the operating region with an optical observation beam path. However, it is also possible to provide a microscope unit which brings digitally acquired images to the display for an observing person. An example of a surgical microscope within the meaning of the invention is the OPMI® Pentem® system, manufactured and distributed by Carl Zeiss Meditec AG. U.S. Pat. No. 4,786,155 has disclosed an optics system of the type set forth at the outset. This optics system is arranged in an operating microscope, which has a device for visualizing structures in the object region by means of light with a wavelength λ≤620 nm. The human eye has comparatively low sensitivity for light at this wavelength. However, this light is only scattered or absorbed a little by the arterial blood in the human body. The operating microscope contains an illumination device, by means of which it is possible to provide light lying in the red and infrared spectral range. In the operating microscope, there is a beam splitter on the side of an afocal magnification system facing away from the object region, above the microscope main objective in the left-hand and right-hand observation beam path, which beam splitter guides the observation light to a camera, by means of which light in the red and infrared spectral range can be detected. The optics system in the operating microscope contains a first optical assembly with an afocal magnification system. This optics system has a second optical assembly, which has the function of an objective and which guides a beam path, which passes through the first optical assembly, from an object region to the image sensor of the camera.
In surgical or operating microscopes, it is desirable, in particular for examining structures in an object region with fluorescing dyes, for an image acquisition system to be able to register not only the visible light but also light from the infrared spectral range.
To this end, conventional operating microscopes have an image acquisition system with different cameras, which are tuned to the visible and infrared spectral ranges (see, for example, DE 10 2006 006 014 A1).